>You are correct with respect to God's purpose for the flood in accordance>with Genesis 6:5. However, God's method was not to "wipe out the people>at that time," as you say. Genesis 6:7 says that God's method of>destruction was to "blot out from the face of the earth man and beast and>creeping things and birds of the air....">>Therefore if God chose to flood the earth, a global flood would be>necessary to accomplish that end.

Ah, you have found the theological flaw in the mankind-obliterating yet
animal-sparing local flood theory. If the flood was local, than ALL the
effects would have to be local. Knowing that the word for earth, erets
in the Hebrew, also means "land" affords the clue. The purpose of the
flood was to "blot out from the face of the LAND man and beast and
creeping things ..." Therefore, if we are consistent, a local flood
exterminates local men, local beasts, and local creeping things. It
would spare distant men, distant beasts, and distant creeping things.